Closed-loop MIMO systems typically transmit channel state information from a receiver to a transmitter over a feedback path. The channel state information may be used to employ beamforming to compensate for the current channel conditions increasing signal-to-noise (SNR) levels at the receiver. In some of these conventional systems, a beamforming matrix may be generated at the receiver based on the channel conditions. Codewords of the codebook may be provided to the transmitter as feedback. The codewords may indicate which beamforming matrix is to be used by the transmitter.
In MIMO systems, the process of determining the beamforming matrix from the channel conditions, searching for the proper codewords, and quantizing the codewords is processing intensive, conventionally requiring many complex multiplication operations. This is particularly an issue in MIMO devices as the number of transmit and receive antennas increase.
Thus, there are general needs for MIMO receivers and methods for providing feedback for beamforming with reduced processing.